The thyroid gland: what to know about hypo- and hyperthyroidism

The thyroid is a small, butterfly-shaped gland at the front of the neck. The hormones it releases set the working pace of nearly every organ — from heart rate and body temperature to weight and mood. When this gland works too little or too much, the effects ripple through the whole body.

Signs of hypothyroidism (underactive)

When the thyroid makes too little hormone, metabolism slows down. Common signs:

• Persistent fatigue and feeling cold
• Unexplained weight gain
• Dry skin and hair loss
• Forgetfulness and low mood
• Constipation and a slow heartbeat

Signs of hyperthyroidism (overactive)

When the thyroid makes too much hormone, the body speeds up. Often seen:

• Palpitations, nervousness, restlessness
• Weight loss despite a good appetite
• Sweating and intolerance to heat
• Hand tremor and insomnia
• Sometimes bulging eyes (Graves' disease)

Causes and risk factors

The most common causes are autoimmune: Hashimoto's thyroiditis leads to an underactive thyroid, Graves' disease to an overactive one. Other factors include iodine deficiency or excess, the post-pregnancy period, certain medicines and family history. Thyroid problems are several times more common in women than in men.

Diagnosis and treatment

Diagnosis is usually made with a simple blood test: TSH, free T4 and T3 levels, plus thyroid antibodies and an ultrasound when needed. Treatment depends on the cause: hypothyroidism is usually managed with a hormone-replacement tablet (levothyroxine), while hyperthyroidism is treated with anti-thyroid drugs, radioactive iodine or surgery. With the right treatment most people live a fully normal life.

When to see a doctor

See an endocrinologist if you have persistent fatigue, unexplained weight change, neck swelling, palpitations or mood changes. Thyroid screening is especially important for women planning a pregnancy.

Frequently asked questions

Does thyroid disease go away?

It often cannot be fully cured, but with medication or other treatments it is brought under complete control and the person lives normally.

Which test do I need?

The first step is a TSH test; based on the result your doctor may order free T4, T3, antibodies or an ultrasound.

Should I take iodine supplements?

Taking iodine on your own can worsen an overactive thyroid. Only take it on a doctor's advice.

This article is for information only and does not replace a doctor's advice.